The following disaster determination system as in Patent Literature 1 and Patent Literature 2 has been known: many sensing terminal devices each including a sensor configured to detect an abnormality in a physical change amount such as occurrence of smoke or harmful gas or thermal elevation and configured to send disaster sensing information when occurrence of disaster has been sensed from the abnormality in the physical change amount are connected together via a network; and when any of the sensing terminal devices dispersedly arranged at different positions sends the disaster sensing information to the network, a disaster occurrence position is determined from the placement position of the sensing terminal device having sent the disaster sensing information, and this prompts the periphery of the disaster occurrence position to evacuate.
In the disaster determination system of Patent Literature 1, many sensing terminal devices each including the sensor configured to sense occurrence of disaster from the abnormality in the physical change amount are connected together via the mesh network, and any of the sensing terminal devices having sensed occurrence of disaster by the sensor sends, by multi-hop communication via the mesh network, the disaster sensing information indicating sensing of occurrence of disaster to the peripheral sensing terminal devices.
The disaster sensing information is transmitted to the peripheral sensing terminal devices based on a routing table formed at each sensing terminal device forming a mesh topology by transmission of a flooding message. Each sensing terminal device having received the disaster sensing information increments the number of hops contained in the disaster sensing information, and then, transfers such disaster sensing information to other peripheral sensing terminal devices. Thus, it can be estimated that a lower number of hops, which is contained in the received disaster sensing information, of any of the relay sensing terminal devices having received the disaster sensing information results in a closer placement position of such a relay sensing terminal device to the placement position of the sensing terminal device having sent the disaster sensing information, i.e., the disaster occurrence position.
Thus, all of the sensing terminal devices having received the disaster sensing information estimate a distance from the disaster occurrence position based on the number of hops contained in the disaster sensing information, and makes a report according to a reporting level corresponding to the distance. This prompts evacuation from the disaster occurrence position as necessary.
In the disaster determination system of Patent Literature 2, many sensing terminal devices each including the sensor configured to detect, e.g., abnormal thermal elevation are dispersedly arranged at the different positions in a building, and each sensing terminal device is connected to a server functioning as a disaster determination processing device configured to determine a disaster status. In the server, an association with the placement position of the sensing terminal device in the building is stored for each sensing terminal device. The server is configured to periodically monitor the detection state of the sensor of each sensing terminal device. When the sensor of any one of the sensing terminal devices or the sensors of any two or more of the sensing terminal devices detect abnormal thermal elevation, the disaster occurrence position is detected from the placement position(s) of the sensing terminal device(s) including the above-described sensor(s).
Thereafter, the server also periodically monitors the detection state of the sensor of each sensing terminal device at a constant interval, thereby repeating similar processing. A disaster expansion direction and a disaster expansion speed are determined from transition of the setting position of the sensing terminal device having sensed occurrence of disaster by the sensor, and an evacuation path and an evacuation direction in the building are notified to each position in the building based on the determination result.